Homogeneous distribution of 211 secondary-phase particles in single-grain melt-grown (Nd,Eu,Gd)Ba2Cu3O7 bulk

The microstructural features of the (Nd,Eu,Gd)Ba2Cu3O7 (NEG) bulks were stu died by optical microscopy in polarized light. The quantitative microstruct ural data were obtained using the image processing system, Image-Pro Plus. Unlike YBa2Cu3Oy melt-processed bulks, the NEG bulk superconductors prepare d by oxygen-controlled-melt-growth process do not exhibit macroscopic 211 s econdary-phase inhomogeneity due to 211 particle pushing. The lowering of i nterface energy and increase of melt viscosity are suggested to be responsi ble for the essential suppression of 211 pushing in NEG melt-grown bulks. T his result opens a way to achieve a homogeneous distribution of the current densities in melt-grown bulk superconductors. (C) 2000 Elsevier Science B. V. All rights reserved.